With two humps that store fat as a source of energy in a desolate, desert climate, camels are a prime example of an animal that calls an extreme environment home. Extreme habitats are environments in which most terrestrial life, including humans, cannot thrive, or in some cases, survive. These harsh areas might have extreme temperatures, exceptionally high pressures, or high acidity. For quite some time, experts believed that such extreme environments could not sustain life. Although most organisms cannot live in such places, some life-forms—known as extremophiles—have adapted to such conditions.
Types of Extreme Habitats
Acidity
In extremely acidic environments, conditions are less than 5 on the pH scale. Essentially, pH levels indicate how acidic, neutral, or basic (alkaline) a system is, with a level of 1 being extremely acidic and a level of 14 being extremely basic. The optimal pH level for a human is around 7.35 to 7.45, which is slightly more basic than a neutral pH level. Extremely acidic habitats are found around the world and can be natural or human-made. Volcanic and geothermal areas that have accumulated a large amount of sulfuric acid produce particularly low pH ecosystems. The Rio Tinto, a river in Spain—known for its deep-red waters—and geothermal sites in the United States' Yellowstone National Park are two examples of such environments. Acidophiles are creatures that can live in acidic environments with pH values ranging from 1 to 5, but they live most optimally at a pH level of 3 or less. Cyanidium caldarium, a type of red algae, is an example of an acidophile. For most animals, high acid levels destroy or damage cells, but this is not the case for acidophiles. They have evolved ways to preserve their cells’ internal pH levels at around 7. Acidophiles can possibly provide some answers to many human needs, including their potential use at acid mine drainage sites for bioremediation—a process where microorganisms are purposely introduced into the environment to break down a contaminant.
The opposite of extreme acidic environments are alkaline environments, which feature natural habitats above a pH level of 9. They are also found around the globe in areas with a high incidence of geothermic or volcanic activity. Yellowstone National Park’s hot springs and the Great Rift Valley in northeastern Africa host extremely alkaline environments. Bacillus halodurans is a type of bacteria that is found in soil and can survive in alkaline environments.
Temperature
Frigid, dry environments, such as those found in polar regions, are extreme habitats that consistently reach temperatures below 5°C (41°F). Studies have discovered that microbes survive and live well in various cold regions, including snow near the South Pole and a few kilometers under the ice in Antarctica. In 2013, a team of scientists discovered a methane-eating bacteria under the ice in Antarctica. These bacteria are a type of psychrophile, meaning they are microorganisms that grow best at temperatures of 15°C (55°F) and below.
Too hot to handle for most, some of the most extreme habitats boast temperatures of more than 40°C (104°F). Many of these sites are associated with geothermal influences, including deep-sea vents and hot springs. Thomas Brock, an American microbiologist, discovered microorganisms surviving and even growing in Yellowstone’s scalding hot springs in 1966. Since then, thermophiles—organisms that require hot water to live—have been found all over the world in hot springs and geysers.
Deserts are also generally considered extreme, hot environments. Animals like the sidewinder snake have learned how to survive in this environment, developing an effective way to slither across the hot sand. They do not move lengthwise, but rather they move their bodies so that only parts of it touch the hot sand at once. This technique limits the amount of body exposed to the burning sand.
What can we learn from extreme environments on Earth?
The animals that have learned to flourish in such harsh habitats can provide answers to important questions. Take Alaska’s wood frogs (Lithobates sylvaticus), for example. These amphibians freeze when winter arrives to this northern U.S. state, but once spring appears many months later, the frogs thaw and continue on with their lives. How can this be? Scientists have discovered that the frogs produce chemicals that prevent ice crystals from forming—an event that would pierce the frogs’ organs and even cells. By studying this species and its unique adaptation to an extremely cold habitat, scientists hope to discover a way to successfully store human organs for an extended amount of time to save for future transplantations. Currently, organs can last no longer than a few hours when refrigerated; they are destroyed when frozen.
Additionally, the miniscule tardigrade, also known as the water bear, is a multi-extremophile. In other words, it can survive in many different kinds of extreme environments, including the high altitudes of the Himalaya, the intense pressure of the deep ocean, and the frigid temperatures of Antarctica. This microscopic water bear could potentially provide insight into the kinds of organisms that could live on planets like Mars since this creature has traveled and survived a 10-day journey to space. Some other extremophiles that survive deep under the earth also provide promise for what life could perhaps look like on Mars.
